A multiple simple adenoma causing severe distortion of the tail base was identified in the cloacal scent gland of a female California Kingsnake (Lampropeltis getulus californiae). In addition to the normal epithelial layer of the gland and the skin, the tumour cells in the glandular epithelium also showed cross immunereactivity with humanised anti-cytokeratin antibody. This is the first description of an adenoma in the scent gland of a reptile species. Neither epithelial nor mesenchymal tumours arising from the scent gland of reptiles have been reported previously. This report also highlights the possible use of humanised antibodies on reptile species for the fast, reliable and specific differential diagnosis of tumours.